Choosing the right rewards credit card and buying through the right shopping portals can save you a lot of money. Credit-Land.com has compiled this giant guide to the best way to pay for purchases at 18 major retailers and depending on your shopping options.

It's compiled as a back-to-school savings guide, so there's also a checklist with which school supplies you can buy at each place, but the cash back or other rewards should still apply if you buy other items.

Not surprisingly, for many of the retailers, you'll save the most with their branded cards, but there are also other rewarding cards you can use for the stores, as the chart shows.

Some helpful tips from Credit-Land.com:

Shopping through online credit card malls can save you up to 10.7% more than shopping in-store or directly at the store's website.

A general cash back credit card is recommended for in-store shopping because you can combine it with store promotions.

For shopping directly on the retailer's site, a store-branded credit card may be best because of the risk of other cash back credit cards not classifying your purchases correctly.